A polarizing plate having at least a polarizer and a polarizing plate protective film is used for various liquid crystal displays, as optical elements thereof.
In addition to an indoor use of the liquid crystal display, such as a TV use, a chance of the outdoor use thereof is increased, for example, use as a mobile device. As a result, development of a liquid crystal display is required, which is impervious to the use under hygrothermal condition than ever before.
Further, a demand for the liquid crystal display to be impervious to more various uses even under unforgiving environment is growing, and durability at a higher level than ever before has been required from year to year.
In addition, the liquid crystal display has been increased in size and decreased in thickness mainly in TV applications in recent years, and thus the polarizing plate having a polarizing plate protective film of a constitutional member is also required to be thinned in accordance therewith.
In the polarizing plate protective film using a cellulose acylate film, it is known that a specific compound is contained in the film, for further improvement in the performance, or in order to solve various problems in the properties as the polarizing plate protective film or the production thereof.
For example, in order to improve polarizer durability, a method of incorporating an organic acid having a pKa of 2 to 7 in a polarizing plate protective film is proposed (see Patent Literature 1).